EP1290466B1 - A user positioning technique for multi-platform communication system - Google Patents
A user positioning technique for multi-platform communication system Download PDFInfo
- Publication number
- EP1290466B1 EP1290466B1 EP01941627A EP01941627A EP1290466B1 EP 1290466 B1 EP1290466 B1 EP 1290466B1 EP 01941627 A EP01941627 A EP 01941627A EP 01941627 A EP01941627 A EP 01941627A EP 1290466 B1 EP1290466 B1 EP 1290466B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- user
- signals
- central hub
- hub
- information
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1853—Satellite systems for providing telephony service to a mobile station, i.e. mobile satellite service
- H04B7/18532—Arrangements for managing transmission, i.e. for transporting data or a signalling message
- H04B7/18534—Arrangements for managing transmission, i.e. for transporting data or a signalling message for enhancing link reliablility, e.g. satellites diversity
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/87—Combinations of radar systems, e.g. primary radar and secondary radar
- G01S13/878—Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1853—Satellite systems for providing telephony service to a mobile station, i.e. mobile satellite service
- H04B7/18545—Arrangements for managing station mobility, i.e. for station registration or localisation
- H04B7/18547—Arrangements for managing station mobility, i.e. for station registration or localisation for geolocalisation of a station
Definitions
- the present invention relates generally to a wireless communication system. More specifically, the present invention relates to a user positioning technique for a multi-platform wireless communication system.
- Document US 5 233 626 B1 shows, further, a repeater diversity spread spectrum communication system and document EP 0 845 874 A2 shows a further geolocation method and apparatus for satellite based telecommunications systems.
- the disclosed mobile communication system can be utilized to break away from the frequency spectrum limitation discussed above and provide much more efficient means to re-use the allocated mobile satellite and wireless spectrum multiple times. By eliminating this frequency spectrum limitation on the operation of multiple satellites, the overall capacity of existing mobile satellite and wireless communication systems can more readily expand.
- the mobile satellite communications system 10 includes a ground telecommunications hub 12, a satellite constellation 14 including a plurality of individual satellites 16, and a plurality of hand-held user terminals 18 such as mobile phones.
- the user terminals 18 can receive signals 20 simultaneously from multiple satellites 16 via their broad beam antennas 22.
- the ground telecommunications hub 12 is in communication with all of the satellites 16 in the satellite constellation 14 individually and simultaneously.
- the hub 12 also pre-processes user signals to compensate for path differentials before sending radiated signals 24 to the satellites 16, as discussed in more detail below.
- the design of the individual satellites 16 can be significantly simplified over those utilized in prior mobile systems because the satellite constellation 14 functions as a sparse radiating array. It is known that the more satellites 16 that are included in a satellite constellation 14, the better the performance the mobile satellite communications system 10 will achieve. Satellites that are simple, small, and provide high performance are preferable. This is because the performance of the system 10 depends more heavily on the satellite constellation 14 than on the individual satellites 16.
- the individual satellites 16 radiate modulated RF power to a chosen field of view ("FOV").
- FOV field of view
- the system 10 is still operable with reduced capacity and no reconfiguration even if one individual satellite 16 is lost for any reason.
- the system 10 features graceful degradation characteristics and provides very high reliability and availability.
- Most of the complexity of the system 10 is located in the ground hubs 12, which locate and track the potential users and perform the major functions of beamforming and filtering, as discussed below.
- the processing performed at the ground telecommunications hub 12 is diagrammatically illustrated.
- the hub 12 tracks, updates, and forward predicts the time variant differential information among various paths between the hub 12 and the intended user terminals 18.
- the accuracy of this information must be within a tenth of an RF wavelength.
- the required path differential accuracy is preferably about ten (10) centimeters.
- the accuracy must be on the order of one (1) centimeter.
- the conventional or GPS techniques are not able to provide the required accuracy.
- the required accuracy of the equivalent path differentials can be provided using two-way active calibration and R2N (two-way ranging navigation) techniques.
- R2N two-way ranging navigation
- An R2N technique is just one technique for obtaining positioning information by which to locate the positioning of the satellites and users precisely using multiple calibration sites and is described in co-pending U.S. Patent Application Serial No. 09/209,062 , entitled “Method and System for Determining a Position of a Transceiver Unit Incorporating Two-Way Ranging Navigation as a Calibration Reference for GPS," and filed on December 10, 1998.
- Other known techniques may also be utilized.
- the ground telecommunications hub 12 has a processing center 26 that processes each signal and is shown in a transmit mode in Figure 2 .
- the hub 12 has the capability to address the plurality of satellites 16 individually through the use of antenna spatial discrimination to provide separate signals to different satellites. Alternatively, code identification can also be used to address different satellites independently.
- the signals from user 1 to user H are input into the processing center 26.
- the position of the various users (1 to H) are determined generally by the circuitry from the various user signals 28, designated by reference number 30.
- the various user signals 28 for user 1 to user H are then combined for transmission to the different satellites 16, as generally indicated by reference number 32. In this case, the signal is sent to N satellites.
- the combined signals are then amplified, filtered, up converted, and then further amplified, as generally indicated by reference number 36.
- These signals are then delivered to a multiple beam antenna 38 where beam-forming processing is done so that the signals can be transmitted to the N satellites via radiating signals 24.
- the beam-forming process can be done in baseband or a low IF frequency band by either digital or analog means. For a low bandwidth (less than a few MHz signals), digital implementation can provide cost advantages.
- the processed signal 24, radiated from the ground hub 12 to each satellite, is amplified, filtered, and then re-radiated by each of the multiple satellites 16 to arrive at a designated user location simultaneously. Consequently, the radiated signals from the multiple satellites will be received coherently by a broad beam antenna 22 of a simple hand held terminal.
- the effect of the spatial processing performed by the processing center 26 is to focus signal strength on the user from multiple satellites 16, which act like sparsely separated portions of a large active reflector. Therefore, the processing on the ground will insert different time delays into the signals 24 which are radiated via various paths. The time delays will be inserted into the signals 24 as if the satellites were located on an ellipsoidal surface, of which the two foci are located exactly at the hub 12 and the designated user 18 positions respectively. In low and middle earth orbit constellations, the users 18 and the hub 12 will always be in the near field of the sparse array.
- Figure 3 illustrates the individual satellites 16 collect RF signals from the same FOV.
- Figure 3 illustrates the return link geometry for receiving signals sent from the user terminals 18 to the ground telecommunications hub 12.
- links there are two groups of links (signals) involved: the links between users 18 and the satellites 16, generally indicated by reference number 40, and those between the satellites 16 and the hub 12, as generally indicated by reference number 42.
- the user antennas 22 preferably are able to illuminate all the satellites 16 involved. This will lead to a constraint on the variation of the gain of the user antenna 22 over the cluster.
- the satellites 16 will amplify the signals 40 received from the users 18 and re-radiate the signals 42 toward the hub 12.
- the hub 12 can receive signals 42 independently, but simultaneously from the satellites 16, and will add the signals 42 from different satellites coherently in the post-processor 44 as illustrated in Figure 4 .
- the signal flows on the block diagram shown in Figure 4 illustrate the receive function of the post-processor 44 and the hub 12.
- the signal flows are reversed from the corresponding ones in Figure 2 . Therefore the receive process will not be reiterated in detail.
- the links 42 from the satellites 16 to the hub 12 are received at the beamformer 38 and then transferred to the receiver and down converters 46 before the signals are separated.
- the signals are separated depending upon the user from which they are received, as generally indicated by reference number 48, and then sent to the specific user 1 through H, as generally indicated by reference number 50. It should be understood that both the receive and transmit function are a necessary part of the pathlink calibration and user positioning.
- the technique of the present invention has been demonstrated to significantly reduce the average side lobe levels. It has been determined that this is due to three factors.
- the proposed architecture is not a periodic array, but rather a randomly spaced sparse array, which has no grating lobes. Although the average side lobe level at a single frequency is relatively high, the level decreases with increasing bandwidth.
- the large sparsely filled array formed by moving satellites is a large extended aperture size. Thus, all of the users on the ground are in the near field of the extended aperture and the wave fronts received by all users are spherical instead of planar. Consequently, dispersion effects become much more pronounced than would be the case in the far field.
- the dispersion grows very fast as a probe is scanned away from the main beam and the dispersion smears the power distribution very effectively over a finite signal bandwidth.
- the communication system is preferably designed with a large frequency bandwidth spectrum. The information signal will therefore be spread over this bandwidth via CDMA or through short duration waveforms for TDMA schemes.
- Figure 5 illustrates diagrammatically the operation of the invention, which allows for the increased re-use of precious frequency spectrum by multiple satellites.
- the advantages provided by this system include no limitation on frequency re-use by additional satellites for point-to-point communications. Rather, the capacity of this system is only limited by total satellite RF power. Further, the preferred embodiment allows for the use of simple and low cost satellite designs, because the more satellites included in the constellation, the better the performance of the overall system. The system also provides high system reliability through graceful degradation, as well as concentrating complex processing at the hubs.
- the preferred embodiment creates demand for a large number of low cost satellites and also uses R2N techniques to perform satellite and user positioning.
- the more users using this system the more accurately the satellite and user positions can be determined.
- the path lengths traversed by the signals are the path lengths traversed by the signals. Therefore, periodic calibration techniques applied directly to those path lengths may be much simpler and more cost effective.
- the system also benefits from large percentage bandwidths available with CDMA and TDMA systems.
- the present invention is divided up into three segments: a hub segment 52 containing the ground telecommunications hub 12, a space segment 54 containing a plurality of individual satellites 16, and a user segment 56, having a plurality of user terminals 18.
- the hub segment also has a processing center 26 and a post-processor 44 for processing the received and transmitted signals.
- the user terminals 18 receive and transmit signals simultaneously from/to multiple satellites 16 via their broad beam antennas.
- the user terminals 18 do not require any capability to separately address the individual satellites 16 of the space segment 54.
- the hub 12 maintains links with each of the satellites 16 in the space segment 54 individually and simultaneously.
- the hub 12 pre-processes the signals intended for each remote user on transmission and post-processes the signals supplied to each local user on reception to compensate for path differentials. These corrections are separately computed and applied to the signals transmitted to or received from each satellite 16 of the space segment 54 for each user.
- Figure 6 illustrates a multi-platform communication system 100 with improved frequency reuse efficiency in accordance with a preferred embodiment of the present invention.
- the system illustrated in Figure 6 uses CDMA coding to subdivide the frequency resource among the various users.
- the system 100 enables a plurality of transponders 102, 104 to receive signals 106, 108 from the ground hub 110 and to transmit the signals 112, 114 at the same frequency with reduced interference to the intended user 116 from signals intended for other users. This is achieved by synchronizing the transmitted signals at the hub in such a way that the intended user 116 will receive all of the signals 112, 114 synchronously and completely in phase.
- the appropriate compensating time delays are calculated and injected into each forward link message at the hub such that the intended user will coherently receive a combined signal from all the transponders as generally indicated at 118.
- the forward link to the intended user 116 follows the sequence of the hub 110 to the first transponder 102 to the user 116 (hub ⁇ trans 1 ⁇ user 1) and also from the hub 110 to the second transponder 104 to the user 116 (hub ⁇ trans 2 ⁇ user 1).
- all intended signals 112, 114 will arrive at the intended user 116 in phase.
- the same signals intended for the intended user 116 will arrive out of phase at a non-intended user 120 and all other non-intended users in the area. This is shown in Figure 7 , which is described below.
- Figure 7 illustrates the operation of the system of Figure 6 with respect to the non-intended user 120.
- the distance between the hub 116 and the first transponder 102 and the distance between the first transponder 102 and the non-intended user 120 (hub ⁇ trans 1 ⁇ user 2) and the distance between the hub 116 and the second transponder 104 and the distance between the second transponder 104 and the non-intended user 120 (hub ⁇ trans 2 ⁇ user 2) are different in this case, even after compensation by the hub. Because of the distance differences, the signals 122, 124 will arrive at the non-intended user 120 at a different times and out-of-phase. The combined signal 126 will thus appear as noise and can be rejected as such by the terminal of the non-intended user 120.
- the transponders 102, 104 can be part of any type of wireless communication system or can even be selected from several such systems.
- a space based system using satellites is illustrated, regional and national tower-based cellular networks for fixed and mobile communications may also be utilized.
- any high altitude platform system such as manned/unmanned airships, balloons, or airplanes may also be utilized.
- any high altitude platform system such as manned/unmanned airships, balloons, or airplanes may also be utilized.
- an unlimited number of transponders may be utilized.
- the multiple transponders are shown as being part of a unitary system, any combination of transponders can be used to transmit signals in accordance with the present invention. For example, a signal may be transmitted to a user through both a space-based system and a high altitude platform system.
- different sets of transponders may be used to communicate with different users. These various sets may overlap in whole, in part or not at all.
- the various CDMA codes for co-located users can be synchronous or asynchronous.
- a synchronous orthogonal code gives an advantage of about 15 dB or better over asynchronous CDMA codes.
- it is hard to synchronize CDMA codes among users.
- asynchronous CDMA communication is assumed.
- multiple transponder nodes increase the system availability and total power resource, it under-utilizes the system's full potential, because there are only a finite number of codes available due to the finite bandwidth available to a system.
- the total bandwidth limits the number of users the system can serve and the system is unable to fully utilize the power and capacity it was designed to handle.
- the system 100 is an asynchronous CDMA system that utilizes imbedded time delays as described in co-pending patent application Serial No. 09/550,505, filed April 17, 2000 and entitled "Coherent Synchronization of Code Division Multiple Access Signals," which is hereby incorporated by reference.
- the signals 112, 114 from each transponder 102, 104 will arrive completely in-phase because appropriate time delays are pre-determined and applied to the signals 112, 114 at the central hub 110, as shown in Figure 9 . It should be understood that ether time delay methods can also be utilized.
- the first user 116 receives signals 112 from each of the transponders 102, 104 using the same code ("code 1").
- the second user 128 receives signals 114 from each of the transponders 102, 104 using the same code (“code 2").
- the central hub 110 determines the time delay between the users and the hub for signals transmitted or received via each transponder and inserts appropriate delays to equalize the total delay via each transponder.
- the intended signals from different transponders will all arrive at the intended user in-phase, while non-intended signals will arrive out of phase.
- the multi-platform system 100 synchronizes all platforms or transponder nodes 102, 104 in reference to each user 116 of the system.
- This synchronization process involves techniques and procedures to synchronize at least three parameters, including timing, phase, and frequency of signals in both the forward link and the return link.
- the bulk of the required processing to accomplish this synchronization is performed at the central hub 110.
- the results of the synchronization process can be used to assist in a determination of user position.
- certain data that has been obtained during the normal synchronization operation can be used to provide information about user positioning that will allow the system to operate in a manner that is more profitable and generates additional revenues. This technique can be accomplished without requiring the dedication of additional resources from the space segment 54 or the user segment 56.
- x y pi z Unknown position vector of user.
- x pi y pi z Known position vector of platform i. n p Number of platforms in the system
- the user position vector to be determined is assumed to be: x y z
- the synchronization process requires the use of a timing delay of the signal along both the forward and return links.
- the timing delay parameter is proportional to range, thus, the above set of equations results in n p equations with three unknowns: x, y and z.
- n p is greater than three (3), then there is a larger number of measurements than are needed to determine the unknown user position. If n p is less than three, this information is still useful for determining user positions when combined with beam direction information in the case of single platform system.
- the frequency parameter information from synchronization can also be used to establish more user positioning information.
- the final synchronization parameter is phase, which also contributes information to user positioning, but in a highly non-linear, modular way.
- the determined phase is related to range as follows: phase ⁇ r i mod ⁇
- the parameters derived in the synchronization process of the operation of the multi-platform system 100 are thus used to determine the user position without the need to collect additional data.
- the preferred method thus tracks the user's position on the system 100 and monitors the time delays for signals transmitted to and received from any user.
- the system 100 can thus adjust the time delays depending upon the coherency of the signals. For any given user there may be any number of different time delays. Thus, based on the user positioning information, the time delay estimates can be modified. This thus allows for the additional utilization of the information that are already available to increase the profitability of the system.
Description
- The present invention relates generally to a wireless communication system. More specifically, the present invention relates to a user positioning technique for a multi-platform wireless communication system.
- Current mobile satellite communication systems, such as Iridium, Globalstar, and ICO, utilize low-cost user terminals as one of their key system features. To maintain communications linkage with these current mobile systems, the system satellites provide multiple beam and high-gain services to the subscribers. The low-cost and lowgain hand-held terminals utilized by the users of these systems, transmit and receive signals to and from high performance satellites which populate almost the entire hemisphere. Some of these current systems require access to at least two satellites to assure a soft hand-over process as the satellites progress from horizon to horizon. As a result, the satellite system becomes more reliable and available as more satellites come into a user's field of view (FOV). The satellite constellations provided by these current systems are thus sized to guarantee a minimum number of satellites within a user's FOV over large coverage areas at all times.
- All of these current mobile satellite communication systems, however, suffer from certain disadvantages. First, they all have limited frequency (the term "frequency" is generalized herein to refer to frequency, time slot or CDMA code) resources. Any given frequency over a given ground position can only be utilized by one user at a time. Thus, if one user accesses a satellite using a particular frequency slot to communicate to his counterpart on network, other satellites and/or users in the same region cannot reuse the same frequency resource in the same local area. In particular, if a nearby secondary user has a handset that requires the same frequency resources as is being utilized by the first user, the second user is unable to access the system, even via different satellites. This is true regardless of the sophistication of the system, including systems that utilize multiple beam satellite designs. Even when multiple satellites are available at a given geographic location, the same frequency spectrum cannot be used by more than one user in a local area. The availability of multiple satellites merely serves to increase the availability of the system to the user. However, the total capacity of these mobile communication satellite systems is still limited by their inefficient usage of the available frequency resources. Thus, the potential growth of these current satellite communication systems is inherently limited.
- Additionally, current telecommunications systems generally allow only mobile-to-hub and hub-to-mobile communications in most low earth orbit and medium earth orbit mobile satellite constellations. Mobile-to-mobile linkages require multiple hops between hubs. This means that two or more frequency resources must be committed by the system to close the links.
- Document
US 5 233 626 B1 shows, further, a repeater diversity spread spectrum communication system and documentEP 0 845 874 A2 shows a further geolocation method and apparatus for satellite based telecommunications systems. - It is clearly desirable to provide a mobile communication satellite system that relaxes the above constraints, and more efficiently utilizes current mobile satellite communication system resources, while also providing much greater opportunity for system growth.
- It is an object of the present invention to provide a wireless communication system with reduced limitations on frequency re-use for point-to-point communications.
- It is another object of the present invention to provide a wireless communication system that utilizes individual transponders and mobile terminals that are relatively simple and of low complexity.
- It is a further object of the present invention to provide a wireless communication system with high system reliability through graceful degradation.
- It is still another object of the present invention to provide a multi-transponder wireless communication system that allows flexible combination of user types.
- It is a related object of the present invention to provide a multi-transponder wireless communication system with better utilization of total system resources.
- It is yet a further object of the present invention to provide a user positioning technique for a multi-platform system that increases the total monetary return.
- In accordance with the above and other objects of the present invention, a method according to
claim 1 and a mobile wireless communication system according to claim 8 are provided. - These and other features of the present invention will become apparent from the following description of the invention, when viewed in accordance with the accompanying drawings and appended claims.
-
-
FIGURE 1 is a schematic illustration of the forward link geometry of a mobile satellite communications system in accordance with the present invention; -
FIGURE 2 is a schematic block diagram illustrating the signal transmission function of a ground telecommunications hub for a wireless communications system in accordance with a preferred embodiment of the present invention; -
FIGURE 3 is a schematic illustration of the return link geometry of a wireless communications system in accordance with a preferred embodiment of the present invention; -
FIGURE 4 is a schematic block diagram illustrating the signal receive function of a ground telecommunications hub for a wireless communications system in accordance with a preferred embodiment of the present invention; -
FIGURE 5 is a schematic flow diagram illustrating the overall architecture for a wireless communications system in accordance with a preferred embodiment of the present invention; -
FIGURE 6 is a schematic illustration of a multi-transponder wireless communication system illustrating signals being received coherently by their intended remote user; -
FIGURE 7 is a schematic illustration of the multi-transponder wireless communication system ofFigure 6 illustrating the same signals being received incoherently by a remote non-intended user; -
FIGURE 8 is a schematic illustration of a conventional approach to an asynchronous CDMA system that may be utilized in accordance with the present invention; and -
FIGURE 9 illustrates a preferred embodiment of the present invention applied to the asynchronous CDMA system ofFigure 8 . - Referring now to the figures, the disclosed mobile communication system can be utilized to break away from the frequency spectrum limitation discussed above and provide much more efficient means to re-use the allocated mobile satellite and wireless spectrum multiple times. By eliminating this frequency spectrum limitation on the operation of multiple satellites, the overall capacity of existing mobile satellite and wireless communication systems can more readily expand.
- Referring now to
Figure 1 , a mobile satellite communication system 10 in accordance with a preferred embodiment of the present invention is illustrated. InFigure 1 , the mobile satellite communications system 10 is illustrated in a forward link mode. The mobile satellite communications system 10 includes aground telecommunications hub 12, asatellite constellation 14 including a plurality ofindividual satellites 16, and a plurality of hand-helduser terminals 18 such as mobile phones. As discussed in more detail below, theuser terminals 18 can receivesignals 20 simultaneously frommultiple satellites 16 via theirbroad beam antennas 22. Theground telecommunications hub 12 is in communication with all of thesatellites 16 in thesatellite constellation 14 individually and simultaneously. Thehub 12 also pre-processes user signals to compensate for path differentials before sendingradiated signals 24 to thesatellites 16, as discussed in more detail below. - In accordance with the preferred embodiment, the design of the
individual satellites 16 can be significantly simplified over those utilized in prior mobile systems because thesatellite constellation 14 functions as a sparse radiating array. It is known that themore satellites 16 that are included in asatellite constellation 14, the better the performance the mobile satellite communications system 10 will achieve. Satellites that are simple, small, and provide high performance are preferable. This is because the performance of the system 10 depends more heavily on thesatellite constellation 14 than on theindividual satellites 16. - In a transmit mode, shown in
Figure 1 , theindividual satellites 16 radiate modulated RF power to a chosen field of view ("FOV"). The system 10 is still operable with reduced capacity and no reconfiguration even if oneindividual satellite 16 is lost for any reason. As a result, the system 10 features graceful degradation characteristics and provides very high reliability and availability. Most of the complexity of the system 10 is located in theground hubs 12, which locate and track the potential users and perform the major functions of beamforming and filtering, as discussed below. - As shown in
Figure 2 , the processing performed at theground telecommunications hub 12 is diagrammatically illustrated. Thehub 12 tracks, updates, and forward predicts the time variant differential information among various paths between thehub 12 and the intendeduser terminals 18. The accuracy of this information must be within a tenth of an RF wavelength. For UHF satellite systems, the required path differential accuracy is preferably about ten (10) centimeters. For L and S band mobile satellite constellations, the accuracy must be on the order of one (1) centimeter. Unfortunately, the conventional or GPS techniques are not able to provide the required accuracy. - In accordance with the present invention, the required accuracy of the equivalent path differentials, including all propagation distortion, can be provided using two-way active calibration and R2N (two-way ranging navigation) techniques. An R2N technique is just one technique for obtaining positioning information by which to locate the positioning of the satellites and users precisely using multiple calibration sites and is described in co-pending
U.S. Patent Application Serial No. 09/209,062 - The
ground telecommunications hub 12 has aprocessing center 26 that processes each signal and is shown in a transmit mode inFigure 2 . Thehub 12 has the capability to address the plurality ofsatellites 16 individually through the use of antenna spatial discrimination to provide separate signals to different satellites. Alternatively, code identification can also be used to address different satellites independently. - As shown in
Figure 2 , assuming that there are "H" users, the signals fromuser 1 to user H, identified generally byreference number 28, are input into theprocessing center 26. The position of the various users (1 to H), are determined generally by the circuitry from the various user signals 28, designated byreference number 30. Thevarious user signals 28 foruser 1 to user H are then combined for transmission to thedifferent satellites 16, as generally indicated byreference number 32. In this case, the signal is sent to N satellites. The combined signals are then amplified, filtered, up converted, and then further amplified, as generally indicated byreference number 36. These signals are then delivered to amultiple beam antenna 38 where beam-forming processing is done so that the signals can be transmitted to the N satellites via radiating signals 24. The beam-forming process can be done in baseband or a low IF frequency band by either digital or analog means. For a low bandwidth (less than a few MHz signals), digital implementation can provide cost advantages. The processedsignal 24, radiated from theground hub 12 to each satellite, is amplified, filtered, and then re-radiated by each of themultiple satellites 16 to arrive at a designated user location simultaneously. Consequently, the radiated signals from the multiple satellites will be received coherently by abroad beam antenna 22 of a simple hand held terminal. - Equivalently, the effect of the spatial processing performed by the
processing center 26 is to focus signal strength on the user frommultiple satellites 16, which act like sparsely separated portions of a large active reflector. Therefore, the processing on the ground will insert different time delays into thesignals 24 which are radiated via various paths. The time delays will be inserted into thesignals 24 as if the satellites were located on an ellipsoidal surface, of which the two foci are located exactly at thehub 12 and the designateduser 18 positions respectively. In low and middle earth orbit constellations, theusers 18 and thehub 12 will always be in the near field of the sparse array. - In a receive mode, shown in
Figure 3 , theindividual satellites 16 collect RF signals from the same FOV.Figure 3 illustrates the return link geometry for receiving signals sent from theuser terminals 18 to theground telecommunications hub 12. As shown inFigure 3 , there are two groups of links (signals) involved: the links betweenusers 18 and thesatellites 16, generally indicated byreference number 40, and those between thesatellites 16 and thehub 12, as generally indicated byreference number 42. For best performance, theuser antennas 22 preferably are able to illuminate all thesatellites 16 involved. This will lead to a constraint on the variation of the gain of theuser antenna 22 over the cluster. - As with the forward link geometry, the
satellites 16 will amplify thesignals 40 received from theusers 18 and re-radiate thesignals 42 toward thehub 12. Thehub 12 can receivesignals 42 independently, but simultaneously from thesatellites 16, and will add thesignals 42 from different satellites coherently in the post-processor 44 as illustrated inFigure 4 . - The signal flows on the block diagram shown in
Figure 4 illustrate the receive function of the post-processor 44 and thehub 12. The signal flows are reversed from the corresponding ones inFigure 2 . Therefore the receive process will not be reiterated in detail. However, thelinks 42 from thesatellites 16 to thehub 12 are received at thebeamformer 38 and then transferred to the receiver and downconverters 46 before the signals are separated. The signals are separated depending upon the user from which they are received, as generally indicated byreference number 48, and then sent to thespecific user 1 through H, as generally indicated byreference number 50. It should be understood that both the receive and transmit function are a necessary part of the pathlink calibration and user positioning. - The technique of the present invention has been demonstrated to significantly reduce the average side lobe levels. It has been determined that this is due to three factors. First, the proposed architecture is not a periodic array, but rather a randomly spaced sparse array, which has no grating lobes. Although the average side lobe level at a single frequency is relatively high, the level decreases with increasing bandwidth. Second, the large sparsely filled array formed by moving satellites is a large extended aperture size. Thus, all of the users on the ground are in the near field of the extended aperture and the wave fronts received by all users are spherical instead of planar. Consequently, dispersion effects become much more pronounced than would be the case in the far field. The dispersion grows very fast as a probe is scanned away from the main beam and the dispersion smears the power distribution very effectively over a finite signal bandwidth. Third, the communication system is preferably designed with a large frequency bandwidth spectrum. The information signal will therefore be spread over this bandwidth via CDMA or through short duration waveforms for TDMA schemes.
-
Figure 5 illustrates diagrammatically the operation of the invention, which allows for the increased re-use of precious frequency spectrum by multiple satellites. The advantages provided by this system include no limitation on frequency re-use by additional satellites for point-to-point communications. Rather, the capacity of this system is only limited by total satellite RF power. Further, the preferred embodiment allows for the use of simple and low cost satellite designs, because the more satellites included in the constellation, the better the performance of the overall system. The system also provides high system reliability through graceful degradation, as well as concentrating complex processing at the hubs. - The preferred embodiment creates demand for a large number of low cost satellites and also uses R2N techniques to perform satellite and user positioning. The more users using this system, the more accurately the satellite and user positions can be determined. However, even more important than the actual positions of the users and satellites are the path lengths traversed by the signals. Therefore, periodic calibration techniques applied directly to those path lengths may be much simpler and more cost effective. Further, the system also benefits from large percentage bandwidths available with CDMA and TDMA systems.
- As shown in
Figure 5 , the present invention is divided up into three segments: ahub segment 52 containing theground telecommunications hub 12, aspace segment 54 containing a plurality ofindividual satellites 16, and auser segment 56, having a plurality ofuser terminals 18. The hub segment also has aprocessing center 26 and a post-processor 44 for processing the received and transmitted signals. - The
user terminals 18 receive and transmit signals simultaneously from/tomultiple satellites 16 via their broad beam antennas. Theuser terminals 18 do not require any capability to separately address theindividual satellites 16 of thespace segment 54. Thehub 12 maintains links with each of thesatellites 16 in thespace segment 54 individually and simultaneously. Thehub 12 pre-processes the signals intended for each remote user on transmission and post-processes the signals supplied to each local user on reception to compensate for path differentials. These corrections are separately computed and applied to the signals transmitted to or received from eachsatellite 16 of thespace segment 54 for each user. -
Figure 6 illustrates amulti-platform communication system 100 with improved frequency reuse efficiency in accordance with a preferred embodiment of the present invention. In particular, the system illustrated inFigure 6 uses CDMA coding to subdivide the frequency resource among the various users. Thesystem 100 enables a plurality oftransponders signals ground hub 110 and to transmit thesignals user 116 from signals intended for other users. This is achieved by synchronizing the transmitted signals at the hub in such a way that the intendeduser 116 will receive all of thesignals - Based on the distances from the
hub 110, to thevarious transponders transponders user 116, the appropriate compensating time delays are calculated and injected into each forward link message at the hub such that the intended user will coherently receive a combined signal from all the transponders as generally indicated at 118. The forward link to the intendeduser 116 follows the sequence of thehub 110 to thefirst transponder 102 to the user 116 (hub →trans 1 → user 1) and also from thehub 110 to thesecond transponder 104 to the user 116 (hub →trans 2 → user 1). Using the correct time delay on each forward link, all intendedsignals user 116 in phase. Conversely, the same signals intended for the intendeduser 116 will arrive out of phase at anon-intended user 120 and all other non-intended users in the area. This is shown inFigure 7 , which is described below. -
Figure 7 , illustrates the operation of the system ofFigure 6 with respect to thenon-intended user 120. The distance between thehub 116 and thefirst transponder 102 and the distance between thefirst transponder 102 and the non-intended user 120 (hub →trans 1 → user 2) and the distance between thehub 116 and thesecond transponder 104 and the distance between thesecond transponder 104 and the non-intended user 120 (hub →trans 2 → user 2) are different in this case, even after compensation by the hub. Because of the distance differences, thesignals non-intended user 120 at a different times and out-of-phase. The combinedsignal 126 will thus appear as noise and can be rejected as such by the terminal of thenon-intended user 120. - It should be understood that the
transponders - As is known, in conventional CDMA single transponder systems, unique CDMA codes are assigned to each user to avoid interference. Similarly, in multi-transponder systems, when two or more transponders are serving the same geographical location, unique CDMA codes must be used to distinguish the various signals and to avoid interference. For example, as shown in
Figure 8 , which illustrates a conventional CDMA multi-transponder system,user 116 must use different codes forsignals different transponders code 1" and "code 3" are assigned to thesame user 116 in this example, with "code 1" being assigned to signal 112 and "code 3" being assigned to signal 114. If bothtransponders code 1", the two receivedsignals user 116 would not be able to decode the signals correctly. Two additional codes must be assigned to each additional user, such asuser 128 who is assignedcodes - The various CDMA codes for co-located users can be synchronous or asynchronous. A synchronous orthogonal code gives an advantage of about 15 dB or better over asynchronous CDMA codes. For multiple platforms, it is hard to synchronize CDMA codes among users. Thus, for the disclosed multi-platform system, asynchronous CDMA communication is assumed. Although multiple transponder nodes increase the system availability and total power resource, it under-utilizes the system's full potential, because there are only a finite number of codes available due to the finite bandwidth available to a system. Thus, the total bandwidth limits the number of users the system can serve and the system is unable to fully utilize the power and capacity it was designed to handle.
- In the preferred embodiment, the
system 100 is an asynchronous CDMA system that utilizes imbedded time delays as described in co-pending patent application Serial No.09/550,505, filed April 17, 2000 signals transponder signals central hub 110, as shown inFigure 9 . It should be understood that ether time delay methods can also be utilized. - As shown, the
first user 116 receivessignals 112 from each of thetransponders code 1"). Similarly, thesecond user 128 receivessignals 114 from each of thetransponders code 2"). Thecentral hub 110 determines the time delay between the users and the hub for signals transmitted or received via each transponder and inserts appropriate delays to equalize the total delay via each transponder. Thus, the intended signals from different transponders will all arrive at the intended user in-phase, while non-intended signals will arrive out of phase. - The
multi-platform system 100 synchronizes all platforms ortransponder nodes user 116 of the system. This synchronization process involves techniques and procedures to synchronize at least three parameters, including timing, phase, and frequency of signals in both the forward link and the return link. The bulk of the required processing to accomplish this synchronization is performed at thecentral hub 110. - In accordance with a preferred embodiment, the results of the synchronization process can be used to assist in a determination of user position. Through this technique, certain data that has been obtained during the normal synchronization operation can be used to provide information about user positioning that will allow the system to operate in a manner that is more profitable and generates additional revenues. This technique can be accomplished without requiring the dedication of additional resources from the
space segment 54 or theuser segment 56. - Three key parameters that are synchronized by the
central hub 110 include timing, phase, and frequency. Further, in accordance with the preferred technique, the following parameters are utilized:
R pi Relative position vector of user with respect to platform i.
rpi Range of user with respect to platform i.
ṙpi Range rate of user with respect to platform i.
np Number of platforms in the system -
-
- As discussed above, the synchronization process requires the use of a timing delay of the signal along both the forward and return links. The timing delay parameter is proportional to range, thus, the above set of equations results in np equations with three unknowns: x, y and z. When np is greater than three (3), then there is a larger number of measurements than are needed to determine the unknown user position. If np is less than three, this information is still useful for determining user positions when combined with beam direction information in the case of single platform system.
-
- This provides an additional set of equations when it is assumed that the position rate can be determined from a position change with respect to time.
-
- The parameters derived in the synchronization process of the operation of the
multi-platform system 100, are thus used to determine the user position without the need to collect additional data. The preferred method thus tracks the user's position on thesystem 100 and monitors the time delays for signals transmitted to and received from any user. Thesystem 100 can thus adjust the time delays depending upon the coherency of the signals. For any given user there may be any number of different time delays. Thus, based on the user positioning information, the time delay estimates can be modified. This thus allows for the additional utilization of the information that are already available to increase the profitability of the system.
Claims (15)
- A method for determining (30) a user position, characterized by:providing a plurality of individual transponding nodes (16; 102, 104);establishing two or more links (20, 24; 40, 42) from a central processing hub (12; 110) with at least one remote user (18; 116) through one or more of said plurality of transponding nodes (16; 102, 104);processing at the central hub (12; 110) user signals (28; 50) transmitted from the central hub (12; 110) and received at the central hub (12; 110), including determining a time delay between the at least one remote user and the central hub (12; 110) for the user signals (28; 50) transmitted or received via each transponding node (16; 102, 104) and inserting appropriate delays to equalize a total delay via each transponding node (16; 102, 104), such that the timing, phase, and frequency of signals (24; 42) in both the forward (24) and return links (42) with respect to said at least one remote user (18; 116) are synchronized for all intermediate transponding nodes (16; 102, 104); anddetermining (30) the position of the remote user (18; 116) based on information retrieved from the synchronization of the respective local user signals (28; 50) and stored on said central hub (12; 110) as timing, phase and/or frequency information relating to said local user signals (28; 50).
- The method of claim 1, characterized by:providing additional information about the position of said at least one remote user (18; 116) based on the frequency information stored at said central hub (12; 110).
- The method of claim 2, characterized by:assisting in determining (30) the position of said at least one remote user (18; 116) based on the phase information stored at said central hub (12; 110).
- The method of claim 1, characterized in that each of said plurality of individual transponding nodes (16; 102, 104) is independently selected from one of the following system types: a space-based system, a high altitude platform system, or a tower based cellular network.
- A mobile wireless communication system (10; 100) with accurate user positioning capabilities, characterized by:a plurality of individual transponding nodes (16; 102, 104);a plurality of mobile terminals (18; 116) each associated with a respective remote user;a central hub (12; 110) for establishing two or more links (20, 24; 40, 42) with one or more of said plurality of mobile terminals (18; 116), each through one or more of said plurality of transponding nodes (16; 102, 104);said central hub (12; 110) processes one or more local user signals (28) from one or more of said remote users (18; 116) transmitted from the ground hub (12; 110) and received at the ground hub (12; 110) by determining a time delay between the at least one remote user and the ground hub (12; 110) for the user signals (28; 50) transmitted or received via each transponding node (16; 102, 104) and inserting appropriate delays to equalize a total delay via each transponding node (16; 102, 104) such that the timing, phase and frequency of signals (24; 42) in both the forward and return links (42) with respect to said at least one remote user (18; 116) are synchronized for all intermediate transponding nodes (16; 102, 104); andwhereby said central hub (12; 110) can determine (30) the position of each of said remote users (18; 116) based on information retrieved from the synchronization of the respective local user signals (28; 50) and stored on said central hub (12; 110) as timing, phase and/or frequency information relating to said local user signals (28; 50).
- The system of claim 8, characterized in that said central hub (12; 110) uses information about the timing of user signals (28) to assist in determining the position of said user.
- The system of claim 8, characterized in that said central hub (12; 110) uses information about the frequency of user signals (28) to assist in determining (30) the position of said user.
- The system of claim 8, characterized in that said central hub (12; 110) uses information about the phase of user signals (28) to assist in determining (30) the position of said user.
- The system of claim 8, characterized in that said central hub (12; 110) uses information about the timing, phase and frequency of user signals (28) to assist in determining (30) the position of said user.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US587759 | 1984-03-12 | ||
US09/587,759 US6920309B1 (en) | 1999-03-18 | 2000-06-06 | User positioning technique for multi-platform communication system |
PCT/US2001/016988 WO2001094969A2 (en) | 2000-06-06 | 2001-05-23 | A user positioning technique for multi-platform communication system |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1290466A2 EP1290466A2 (en) | 2003-03-12 |
EP1290466B1 true EP1290466B1 (en) | 2010-04-07 |
Family
ID=24351092
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP01941627A Expired - Lifetime EP1290466B1 (en) | 2000-06-06 | 2001-05-23 | A user positioning technique for multi-platform communication system |
Country Status (5)
Country | Link |
---|---|
US (1) | US6920309B1 (en) |
EP (1) | EP1290466B1 (en) |
DE (1) | DE60141751D1 (en) |
ES (1) | ES2343835T3 (en) |
WO (1) | WO2001094969A2 (en) |
Families Citing this family (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6337980B1 (en) | 1999-03-18 | 2002-01-08 | Hughes Electronics Corporation | Multiple satellite mobile communications method and apparatus for hand-held terminals |
US8446321B2 (en) | 1999-03-05 | 2013-05-21 | Omnipol A.S. | Deployable intelligence and tracking system for homeland security and search and rescue |
US7908077B2 (en) | 2003-06-10 | 2011-03-15 | Itt Manufacturing Enterprises, Inc. | Land use compatibility planning software |
US7667647B2 (en) | 1999-03-05 | 2010-02-23 | Era Systems Corporation | Extension of aircraft tracking and positive identification from movement areas into non-movement areas |
US7889133B2 (en) | 1999-03-05 | 2011-02-15 | Itt Manufacturing Enterprises, Inc. | Multilateration enhancements for noise and operations management |
US7739167B2 (en) | 1999-03-05 | 2010-06-15 | Era Systems Corporation | Automated management of airport revenues |
US7570214B2 (en) | 1999-03-05 | 2009-08-04 | Era Systems, Inc. | Method and apparatus for ADS-B validation, active and passive multilateration, and elliptical surviellance |
US7777675B2 (en) | 1999-03-05 | 2010-08-17 | Era Systems Corporation | Deployable passive broadband aircraft tracking |
US8203486B1 (en) | 1999-03-05 | 2012-06-19 | Omnipol A.S. | Transmitter independent techniques to extend the performance of passive coherent location |
US7782256B2 (en) | 1999-03-05 | 2010-08-24 | Era Systems Corporation | Enhanced passive coherent location techniques to track and identify UAVs, UCAVs, MAVs, and other objects |
US7257418B1 (en) | 2000-08-31 | 2007-08-14 | The Directv Group, Inc. | Rapid user acquisition by a ground-based beamformer |
US6763242B1 (en) | 2000-09-14 | 2004-07-13 | The Directv Group, Inc. | Resource assignment system and method for determining the same |
US7187949B2 (en) | 2001-01-19 | 2007-03-06 | The Directv Group, Inc. | Multiple basestation communication system having adaptive antennas |
US8396513B2 (en) | 2001-01-19 | 2013-03-12 | The Directv Group, Inc. | Communication system for mobile users using adaptive antenna |
US7809403B2 (en) | 2001-01-19 | 2010-10-05 | The Directv Group, Inc. | Stratospheric platforms communication system using adaptive antennas |
US7555297B2 (en) * | 2002-04-17 | 2009-06-30 | Aerovironment Inc. | High altitude platform deployment system |
US20040137840A1 (en) * | 2003-01-15 | 2004-07-15 | La Chapelle Michael De | Bi-directional transponder apparatus and method of operation |
US7965227B2 (en) | 2006-05-08 | 2011-06-21 | Era Systems, Inc. | Aircraft tracking using low cost tagging as a discriminator |
GB2542163B (en) | 2015-09-10 | 2021-07-07 | Stratospheric Platforms Ltd | Lightweight process and apparatus for communicating with user antenna phased arrays |
EP3355079B8 (en) | 2017-01-25 | 2023-06-21 | Airbus Defence and Space GmbH | Method for each of a plurality of satellites of a secondary global navigation satellite system in a low earth orbit |
Family Cites Families (92)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2470787A (en) | 1944-05-04 | 1949-05-24 | Paul W Nosker | System for determining the position or path of an object in space |
US3384891A (en) | 1965-02-11 | 1968-05-21 | Gen Electric | Method and system for long distance navigation and communication |
DE1591517B1 (en) | 1967-07-21 | 1971-08-05 | Siemens Ag | Radio location method by measuring the transit time to vehicles with transponders via earth satellites |
US3720953A (en) | 1972-02-02 | 1973-03-13 | Hughes Aircraft Co | Dual polarized slot elements in septated waveguide cavity |
US4161730A (en) | 1977-10-17 | 1979-07-17 | General Electric Company | Radio determination using satellites transmitting timing signals with correction by active range measurement |
US4161734A (en) | 1977-10-17 | 1979-07-17 | General Electric Company | Position surveillance using one active ranging satellite and time of arrival of a signal from an independent satellite |
US4359733A (en) | 1980-09-23 | 1982-11-16 | Neill Gerard K O | Satellite-based vehicle position determining system |
DE3301613A1 (en) | 1983-01-19 | 1984-07-19 | Standard Elektrik Lorenz Ag, 7000 Stuttgart | POSITION DETECTION SYSTEM |
US4635063A (en) | 1983-05-06 | 1987-01-06 | Hughes Aircraft Company | Adaptive antenna |
NL8402497A (en) | 1984-08-14 | 1986-03-03 | Philips Nv | VEHICLE NAVIGATION SYSTEM EQUIPPED WITH AN ADAPTIVE INSURANCE NAVIGATION SYSTEM BASED ON MEASUREMENT OF THE SPEED AND CROSS-GEAR ACCELERATION OF THE VEHICLE AND PROVIDED WITH A CORRECTION UNIT FOR CORRECTING THE MEASURED VALUES. |
US4819227A (en) | 1986-08-14 | 1989-04-04 | Hughes Aircraft Company | Satellite communications system employing frequency reuse |
US5006855A (en) | 1986-08-20 | 1991-04-09 | The Mitre Corporation | Ranging and processing system for mobile surveillance and data link |
JPS63253278A (en) | 1987-04-10 | 1988-10-20 | Sony Corp | Position measuring method using satellite |
US5099245A (en) | 1987-10-23 | 1992-03-24 | Hughes Aircraft Company | Vehicle location system accuracy enhancement for airborne vehicles |
US4979170A (en) | 1988-01-19 | 1990-12-18 | Qualcomm, Inc. | Alternating sequential half duplex communication system |
GB2215932A (en) | 1988-03-26 | 1989-09-27 | Gec Traffic Automation | Radio position finding system |
US5126748A (en) | 1989-12-05 | 1992-06-30 | Qualcomm Incorporated | Dual satellite navigation system and method |
US5017927A (en) | 1990-02-20 | 1991-05-21 | General Electric Company | Monopulse phased array antenna with plural transmit-receive module phase shifters |
US4994809A (en) | 1990-03-07 | 1991-02-19 | Hughes Aircraft Company | Polystatic correlating radar |
JP2979582B2 (en) | 1990-05-23 | 1999-11-15 | ソニー株式会社 | Transmission system |
US5506864A (en) | 1990-12-05 | 1996-04-09 | Interdigital Technology Corporation | CDMA communications and geolocation system and method |
US5218619A (en) | 1990-12-17 | 1993-06-08 | Ericsson Ge Mobile Communications Holding, Inc. | CDMA subtractive demodulation |
US5077562A (en) | 1990-12-24 | 1991-12-31 | Hughes Aircraft Company | Digital beam-forming technique using temporary noise injection |
FR2681199B1 (en) | 1991-09-11 | 1993-12-03 | Agence Spatiale Europeenne | METHOD AND DEVICE FOR MULTIPLEXING DATA SIGNALS. |
US5365447A (en) | 1991-09-20 | 1994-11-15 | Dennis Arthur R | GPS and satelite navigation system |
AU3324893A (en) | 1991-12-16 | 1993-07-19 | Omnipoint Corporation | Spread-spectrum data publishing system |
US5550809A (en) | 1992-04-10 | 1996-08-27 | Ericsson Ge Mobile Communications, Inc. | Multiple access coding using bent sequences for mobile radio communications |
US5278863A (en) | 1992-04-10 | 1994-01-11 | Cd Radio Incorporated | Radio frequency broadcasting systems and methods using two low-cost geosynchronous satellites |
US5485485A (en) | 1992-04-10 | 1996-01-16 | Cd Radio Inc. | Radio frequency broadcasting systems and methods using two low-cost geosynchronous satellites and hemispherical coverage antennas |
US5233626A (en) | 1992-05-11 | 1993-08-03 | Space Systems/Loral Inc. | Repeater diversity spread spectrum communication system |
US5387916A (en) | 1992-07-31 | 1995-02-07 | Westinghouse Electric Corporation | Automotive navigation system and method |
US5430657A (en) | 1992-10-20 | 1995-07-04 | Caterpillar Inc. | Method and apparatus for predicting the position of a satellite in a satellite based navigation system |
US5739785A (en) | 1993-03-04 | 1998-04-14 | Trimble Navigation Limited | Location and generation of high accuracy survey control marks using satellites |
US5379320A (en) | 1993-03-11 | 1995-01-03 | Southern California Edison Company | Hitless ultra small aperture terminal satellite communication network |
US5423059A (en) | 1993-07-29 | 1995-06-06 | Motorola Inc. | Method for enhancing signal quality in a simulcast communication system |
US5444450A (en) | 1993-08-11 | 1995-08-22 | Motorola, Inc. | Radio telecommunications system and method with adaptive location determination convergence |
US5572216A (en) | 1993-11-19 | 1996-11-05 | Stanford Telecommunications, Inc. | System for increasing the utility of satellite communication systems |
US6020845A (en) | 1993-11-19 | 2000-02-01 | Stanford Telecommunications, Inc. | Satellite for increasing the utility of satellite communication systems |
US5410314A (en) | 1993-11-30 | 1995-04-25 | University Corporation For Atmospheric Research | Bistatic multiple-doppler radar network |
US6195555B1 (en) * | 1994-01-11 | 2001-02-27 | Ericsson Inc. | Method of directing a call to a mobile telephone in a dual mode cellular satellite communication network |
US5619503A (en) * | 1994-01-11 | 1997-04-08 | Ericsson Inc. | Cellular/satellite communications system with improved frequency re-use |
US5589834A (en) | 1994-04-22 | 1996-12-31 | Stanford Telecommunications, Inc. | Cost effective geosynchronous mobile satellite communication system |
US5859874A (en) | 1994-05-09 | 1999-01-12 | Globalstar L.P. | Multipath communication system optimizer |
GB2321831B (en) | 1994-07-22 | 1999-02-17 | Int Mobile Satellite Org | Satellite communication method and apparatus |
US5592471A (en) | 1995-04-21 | 1997-01-07 | Cd Radio Inc. | Mobile radio receivers using time diversity to avoid service outages in multichannel broadcast transmission systems |
US5508708A (en) | 1995-05-08 | 1996-04-16 | Motorola, Inc. | Method and apparatus for location finding in a CDMA system |
JP2661589B2 (en) | 1995-05-22 | 1997-10-08 | 日本電気株式会社 | Dynamic queuing method by GPS |
AU700251B2 (en) | 1995-06-06 | 1998-12-24 | Globalstar L.P. | Satellite repeater diversity resource management system |
US5525995A (en) | 1995-06-07 | 1996-06-11 | Loral Federal Systems Company | Doppler detection system for determining initial position of a maneuvering target |
FR2737627B1 (en) | 1995-08-02 | 1997-10-03 | Europ Agence Spatiale | RADIO SIGNAL TRANSMISSION SYSTEM VIA A GEOSTATIONARY COMMUNICATION SATELLITE, ESPECIALLY FOR COMMUNICATIONS WITH PORTABLE MOBILE TERMINALS |
US5612701A (en) | 1995-09-18 | 1997-03-18 | Motorola, Inc. | Adaptive beam pointing method and apparatus for a communication system |
US5644572A (en) | 1995-10-03 | 1997-07-01 | Motorola, Inc. | Method and apparatus for approximating propagation delay for use in transmission compensation to orbiting satellites |
GB2339099B (en) | 1995-10-24 | 2000-05-31 | Inmarsat Ltd | Satellite radiodetermination |
GB2307621B (en) | 1995-11-21 | 1997-12-03 | At & T Corp | Cdma air interface for radio local loop system |
US5907813A (en) * | 1995-11-30 | 1999-05-25 | Qualcomm Incorporated | Signal acquisition in a wireless communication system by transmitting repeated access probes from a terminal to a hub |
US5909460A (en) | 1995-12-07 | 1999-06-01 | Ericsson, Inc. | Efficient apparatus for simultaneous modulation and digital beamforming for an antenna array |
US5812961A (en) | 1995-12-28 | 1998-09-22 | Trimble Navigation Limited | Method and reciever using a low earth orbiting satellite signal to augment the global positioning system |
US5917447A (en) | 1996-05-29 | 1999-06-29 | Motorola, Inc. | Method and system for digital beam forming |
US5878034A (en) | 1996-05-29 | 1999-03-02 | Lockheed Martin Corporation | Spacecraft TDMA communications system with synchronization by spread spectrum overlay channel |
US5864579A (en) | 1996-07-25 | 1999-01-26 | Cd Radio Inc. | Digital radio satellite and terrestrial ubiquitous broadcasting system using spread spectrum modulation |
US5945948A (en) | 1996-09-03 | 1999-08-31 | Motorola, Inc. | Method and apparatus for location finding in a communication system |
US5920284A (en) | 1996-09-30 | 1999-07-06 | Qualcomm Incorporated | Ambiguity resolution for ambiguous position solutions using satellite beams |
GB2318482B (en) | 1996-10-16 | 2001-06-13 | Ico Services Ltd | Communication system |
US5856804A (en) | 1996-10-30 | 1999-01-05 | Motorola, Inc. | Method and intelligent digital beam forming system with improved signal quality communications |
US5844521A (en) | 1996-12-02 | 1998-12-01 | Trw Inc. | Geolocation method and apparatus for satellite based telecommunications system |
US5956619A (en) | 1996-12-12 | 1999-09-21 | Globalstar L.P. | Satellite controlled power control for personal communication user terminals |
US6151308A (en) | 1996-12-30 | 2000-11-21 | Motorola, Inc. | Elevated communication hub and method of operation therefor |
US5949766A (en) | 1996-12-30 | 1999-09-07 | Motorola, Inc. | Ground device for communicating with an elevated communication hub and method of operation thereof |
US5903549A (en) | 1997-02-21 | 1999-05-11 | Hughes Electronics Corporation | Ground based beam forming utilizing synchronized code division multiplexing |
DE69830936T2 (en) | 1997-02-21 | 2006-04-20 | Hughes Electronics Corp., El Segundo | Method and device for determining the position of the transceiver system by means of two-way distance determination in a polystatic satellite configuration with ground radar |
US6377208B2 (en) | 1997-02-21 | 2002-04-23 | Hughes Electronics Corporation | Method and system for determining a position of a transceiver unit utilizing two-way ranging in a polystatic satellite configuration |
US5969674A (en) * | 1997-02-21 | 1999-10-19 | Von Der Embse; Urban A. | Method and system for determining a position of a target vehicle utilizing two-way ranging |
US5918157A (en) | 1997-03-18 | 1999-06-29 | Globalstar L.P. | Satellite communications system having distributed user assignment and resource assignment with terrestrial gateways |
US5790070A (en) | 1997-05-05 | 1998-08-04 | Motorola, Inc. | Network and method for controlling steerable beams |
US6138012A (en) | 1997-08-04 | 2000-10-24 | Motorola, Inc. | Method and apparatus for reducing signal blocking in a satellite communication system |
US5973647A (en) | 1997-09-17 | 1999-10-26 | Aerosat Corporation | Low-height, low-cost, high-gain antenna and system for mobile platforms |
AU742826B2 (en) | 1997-10-14 | 2002-01-10 | Qualcomm Incorporated | Methods and apparatus for measuring nonlinear effects in a communication system and for selecting channels on the basis of the results |
US6243587B1 (en) * | 1997-12-10 | 2001-06-05 | Ericsson Inc. | Method and system for determining position of a mobile transmitter |
US6289211B1 (en) * | 1998-03-26 | 2001-09-11 | Erksson Inc | Method for determining the position of a mobile station |
US6111542A (en) | 1998-04-06 | 2000-08-29 | Motorola, Inc. | Rotating electronically steerable antenna system and method of operation thereof |
US6119016A (en) * | 1998-06-10 | 2000-09-12 | Lucent Technologies, Inc. | Synchronizing base stations in a wireless telecommunications system |
JP3316561B2 (en) | 1998-07-06 | 2002-08-19 | 株式会社村田製作所 | Array antenna device and wireless device |
US6298238B1 (en) | 1998-09-09 | 2001-10-02 | Qualcomm Incorporated | Fast user terminal position determination in a satellite communications system |
US6229477B1 (en) | 1998-10-16 | 2001-05-08 | Hughes Electronics Corporation | Method and system for determining a position of a communication satellite utilizing two-way ranging |
US6337980B1 (en) | 1999-03-18 | 2002-01-08 | Hughes Electronics Corporation | Multiple satellite mobile communications method and apparatus for hand-held terminals |
US6246363B1 (en) | 1998-12-10 | 2001-06-12 | Hughes Electronics Corporation | Method and system for incorporating two-way ranging navigation as a calibration reference for GPS |
US6266533B1 (en) * | 1998-12-11 | 2001-07-24 | Ericsson Inc. | GPS assistance data for positioning of mobiles with built-in GPS |
US6208626B1 (en) | 1998-12-24 | 2001-03-27 | Charles R. Brewer | Real-time satellite communication system using separate control and data transmission paths |
US6480788B2 (en) | 1999-07-12 | 2002-11-12 | Eagle-Eye, Inc. | System and method for fast acquisition reporting using communication satellite range measurement |
US6963548B1 (en) | 2000-04-17 | 2005-11-08 | The Directv Group, Inc. | Coherent synchronization of code division multiple access signals |
DE60127758T2 (en) | 2000-05-22 | 2007-12-27 | Hughes Electronics Corp., El Segundo | Wireless communication system with multiple platforms for different types of users |
US6388615B1 (en) | 2000-06-06 | 2002-05-14 | Hughes Electronics Corporation | Micro cell architecture for mobile user tracking communication system |
-
2000
- 2000-06-06 US US09/587,759 patent/US6920309B1/en not_active Expired - Lifetime
-
2001
- 2001-05-23 WO PCT/US2001/016988 patent/WO2001094969A2/en active Application Filing
- 2001-05-23 ES ES01941627T patent/ES2343835T3/en not_active Expired - Lifetime
- 2001-05-23 EP EP01941627A patent/EP1290466B1/en not_active Expired - Lifetime
- 2001-05-23 DE DE60141751T patent/DE60141751D1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
ES2343835T3 (en) | 2010-08-11 |
DE60141751D1 (en) | 2010-05-20 |
EP1290466A2 (en) | 2003-03-12 |
WO2001094969A2 (en) | 2001-12-13 |
WO2001094969A3 (en) | 2002-03-28 |
US6920309B1 (en) | 2005-07-19 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US8223733B2 (en) | Multi-platform wireless communication system for a variety of different user types | |
EP1290466B1 (en) | A user positioning technique for multi-platform communication system | |
RU2153226C2 (en) | Device for controlling distributed signal transmission system using satellite retransmitters | |
KR101822369B1 (en) | High-capacity hybrid terrestrial/satellite cellular radio communication system | |
US20030208317A1 (en) | Position location of multiple transponding platforms and users using two-way ranging as a calibration reference for GPS | |
EP2735883A1 (en) | Method of geo localization of a terminal sending a single signal to a satellite | |
EP1158698B1 (en) | A multi-platform wireless communication system for a variety of different user types | |
US6990314B1 (en) | Multi-node point-to-point satellite communication system employing multiple geo satellites | |
US20020190897A1 (en) | Information terminal with positioning function, positioning system, method of positioning, storage medium, and computer program product | |
US6895217B1 (en) | Stratospheric-based communication system for mobile users having adaptive interference rejection | |
EP1232579B1 (en) | Multi-node wireless communication system with multiple transponding platforms | |
EP1208660B1 (en) | Multi-node point-to-point satellite communication system employing multiple geo satellites | |
EP1208659B1 (en) | Resource allocation method in a satellite diversity system | |
US7215954B1 (en) | Resource allocation method for multi-platform communication system | |
US7089000B1 (en) | Multi-node wireless communication system with multiple transponding platforms | |
Gamache | The use of C-band satellites for low cost, low data rate mobile applications | |
Monte et al. | Mobile telephony through LEO satellites: To OBP or not | |
GB2353159A (en) | Position determination in multi-beam satellite | |
Demirev | SCP-RPSC-the key technology in the next generation steerable lines for satellite communications | |
Siep et al. | 2.6 Wireless Personal Area Network Communications: An Application Overview |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 20020126 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE TR |
|
RBV | Designated contracting states (corrected) |
Designated state(s): DE ES FR GB IT |
|
17Q | First examination report despatched |
Effective date: 20090709 |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: THE DIRECTV GROUP, INC. |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE ES FR GB IT |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: FG4D |
|
REF | Corresponds to: |
Ref document number: 60141751 Country of ref document: DE Date of ref document: 20100520 Kind code of ref document: P |
|
REG | Reference to a national code |
Ref country code: ES Ref legal event code: FG2A Ref document number: 2343835 Country of ref document: ES Kind code of ref document: T3 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed |
Effective date: 20110110 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20100407 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: PLFP Year of fee payment: 16 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: ES Payment date: 20160512 Year of fee payment: 16 Ref country code: DE Payment date: 20160520 Year of fee payment: 16 Ref country code: GB Payment date: 20160520 Year of fee payment: 16 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20160520 Year of fee payment: 16 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R119 Ref document number: 60141751 Country of ref document: DE |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20170523 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST Effective date: 20180131 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20170523 Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20171201 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20170531 |
|
REG | Reference to a national code |
Ref country code: ES Ref legal event code: FD2A Effective date: 20180705 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: ES Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20170524 |